Introduction :
Security isn't just about fixing vulnerabilities it's about understanding where risks come from, and eliminating entire classes of threats before they become issues. Threat modeling helps teams do exactly that.
This guide offers a simple, repeatable process to help you start threat modeling, even if you're not a security expert.
🎯 Step 1: Define What You’re Protecting
Start by answering:
- What is your product or system?
- What are the key features (e.g., login, file uploads, integrations)?
- What data do you store or process? (e.g., PII, financial, passwords)
- Who are the users? (e.g., admins, customers, third parties)
Tip: Don’t overthink it. Just write down what the product does and who interacts with it.
🎯 Step 2: Identify What Can Go Wrong
For each part of the system, ask:
- Authentication: Can someone bypass login? Abuse password reset?
- Authorization: Can users access or modify data they shouldn’t?
- Input/Output: Can attackers inject malicious data (XSS, SQLi)?
- Integrations: Can external systems be abused (SSRF, CSRF)?
- Infrastructure: Are internal resources exposed (e.g., S3 buckets)?
- Abuse: Can bots, brute force, or scraping overload your system?
- What about your internal Systems like admin portal or any internal system are they behind VPN or or zero trust or expose to internet ?
- Who have access to these system ?
- Do you have an audit log for them?
💡 Think like an attacker: "If I wanted to break this, what would I try?"
🔐 Step 3: Look for Trust Boundaries
A trust boundary is where one system or user hands control to another.
Examples:
- From unauthenticated to authenticated user
- From user to admin role
- From frontend to backend
- From your app to a third-party API
- From your third party to your application
These boundaries are prime targets for attacks. They deserve extra attention in your threat model.
🧱 Step 4: Prioritize the Risks
Not all risks are equal. Ask:
- What’s the impact if this is exploited? (e.g., data leak, account takeover)
- What’s the likelihood? (Is it easy to discover or abuse?)
- Are there existing controls?
Focus on high-impact, high-likelihood risks first. Document the rest for later review.
🔁 Step 5: Mitigate and Revisit
For each risk, decide:
- Can we prevent it (e.g., access control)?
- Can we detect it (e.g., audit logs)?
- Can we respond (e.g., disable account, alert team)?
Threat models should be living documents. Revisit them:
- Before new feature releases
- After incidents
- During security reviews
🧰 Tools That Help
While threat modeling is mostly about thinking, these tools can help:
- OWASP Threat Dragon – lightweight visual threat modeling tool
- Checklists – like STRIDE or OWASP ASVS to structure your review
Final Advice
- You don’t need a security team to start threat modeling
- Even informal modeling catches 80% of critical issues early
- Make it a habit: include threat modeling in design or sprint planning
- During a security assessment, share known risks with your testing partner to help them focus on the most critical areas.